1. Field of the Invention
The present invention relates to pianos, and more particularly, to pianos having lever action piano keys which are coupled to displace variable mass hammers for striking variable mass piano strings.
2. Description of the Prior Art
The prior art discloses many different structures which are intended to vary the force required to cause a hammer to strike a piano string. This process is generally referred to as lightening the touch of the piano. U.S. Pat. No. 1,224,994 (Anelli) discloses a specific piano keyboard design which permits the balance rail to be displaced fore and aft to move the pivot point of all piano keys in unison to modify the touch of a piano. In this embodiment, the length of both piano key lever arms is modified as the balance rail if repositioned. Adjustment of the balance rail position permits the touch of the piano to either be increased or decreased.
U.S. Pat. No. 777,133 (Olsson) discloses an improvement for a pipe organ which permits the organ key fulcrum point to be modified to vary the force required to open a selected organ valve. The fulcrum point for each organ key can be individually adjusted to provide the desired feel.
U.S. Pat. No. 619,964 (Kringel) discloses a touch regulator for a piano action. FIG. 8 and the last column of the disclosure of this patent specifically relates to modifying the touch or feel of a grand piano action. Pringle discloses a user-adjustable system which horizontally displaces a series of weights of predetermined distance. A single weight is coupled to the rear side of each piano key and simultaneously displaces all piano key weights a uniform distance by the user-controlled adjusting rod in order to modify the playing forces of all keys simultaneously.
U.S. Pat. No. 2,466,498 (Smith) discloses a grand piano action which includes a pivotable knuckle to reduce the friction between the hammer and the hammer displacing escapement. The Smith patent also discloses a spring which is coupled to the hammer and to the hammer actuating structure. This spring provides an upward biasing force which reduces the hammer actuating force and thereby modifies the touch of the piano.
The following techniques are well known to those skilled in the art and are intended to reduce the touch of the piano action. Moving lead weights disposed within the interior of the ivory covered ends of the piano keys; adding or substracting lead from the piano keys; elevating the damper lever; filing felt from the piano hammers to reduce the overall mass of the piano hammers; reducing the tension on the repetition spring; and elevating the capstan screw. Each of these prior art techniques accomplishes its purpose to a limited extent, but typically also reduces the performance of the piano. For example, filing felt from a piano hammer makes the hammer felt harder and smaller than desired. Reducing the tension of the repetition spring causes the repetition to be less certain. Elevating the capstan raises the hammer line and therefore reduces the hammer throw. Adding lead to a piano key increases the inertia of the piano key and reduces the speed of the hammer return, substantially affecting the playing characteristics or the piano.
In present day grand pianos the lowest bass key requires a fifty gram force to actuate the hammer, while the hammer commences a return movement to its resting position when the key deflecting force is reduced to eighteen grams. At the highest treble key, these factors are changed as follows: 38 grams down/24 grams up.
The playing forces recited above for a grand piano are substantially in excess for the playing forces for an upright piano in which the hammers are deflected horizontally and are not elevated against the force of gravity as is the case with a grand piano. For that reason, non-professional musicians have greatly difficulty playing a grand piano well. Professional musicians must practic four to five hours each day to maintain their hand and finger muscles in a state which can properly actuate the keys in a grand piano. A second disadvantage of a grand piano which is not nearly as evident as in an upright piano is that the playing forces described above vary from fifty grams at the low end of the scales to 38 grams at the high end of the scale. This varying playing force makes it extremely difficult for anyone but a highly experiences, professional pianist to maintain a uniform dynamic range as the piano is played or to produce a wide dynamic range.